Question

A glass tube of radius 0.8 cm floats vertical in water. What mass of lead pellets would cause the tube to sink a further 3 cm?

Answer 1

Extra weight=extra upthrust on extra immersed volume.
$\therefore$ $\left(\Delta m\right)g=\left(\pi r^2\Delta h\right){\rho }_{w}g$
$\therefore$ $\Delta m=\pi r^2\Delta h{\rho }_w$
$=\left(\pi \right){\left(0.8\right)}^2\left(3\right)\left(1\right)$
$=6.03$ g